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Mitochondrial tolerance to single and repeat exposure to simulated sunlight in human epidermal and dermal skin cells
1Mitochondrial Biology & Radiation Research Centre, Dept. of Life Sciences, Institute of Technology Sligo, Ash Lane, Sligo, Ireland.
Background:
Sunlight represents the primary threat to mitochondrial integrity in skin given the unique nature of the mitochondrial genome and its proximity to the electron transport chain. The accumulation of mitochondrial DNA (mtDNA) mutations is a key factor in many human pathologies and this is linked to key roles of mitochondrial function in terms of energy production and cell regulation.
Objective:
The main objective of this study was to evaluate solar radiation induced changes in mitochondrial integrity, function and dynamics in human skin cells using a Q-Sun solar simulator to deliver a close match to the intensity of summer sunlight.
Methods:
Spontaneously immortalised human skin epidermal keratinocytes (HaCaT) and Human Dermal Fibroblasts (HDFn) were divided into two groups. Group A were irradiated once and Group B twice 7days apart and evaluated using cell survival, viability and mitochondrial membrane potential (MMP) and mass at 1, 4 and 7days post one exposure for Group A and 1, 4, 7 and 14days post second exposure for Group B.
Results:
Viability and survival of HaCaT and HDFn cells decreased after repeat exposure to Simulated Sunlight Irradiation (SSI) with no recovery. HDFn cells showed no loss in MMP after one or two exposures to SSI compared to HaCaT cells which showed a periodic loss of MMP after one exposure with a repeat exposure causing a dramatic decrease from which cells did not recover. Mitochondrial Mass in exposed HDFn cells was consistent with control after one or two exposures to SSI; however mitochondrial mass was significantly decreased in HaCaT cells.
Conclusion:
Data presented here suggests that mitochondria in epidermal cells are more sensitive to sunlight damage compared to mitochondria in dermal cells, despite their origin, confirming a skin layer specific sensitivity to sunlight, but not as expected.
Insights
Sunlight damages skin cell mitochondria, with epidermal cells showing greater sensitivity than dermal cells after simulated solar radiation. Repeat exposures led to decreased viability and no recovery in both cell types.
Area of Science:
- Dermatology
- Cell Biology
- Photobiology
Background:
- Sunlight poses a significant threat to mitochondrial integrity in skin cells.
- Accumulated mitochondrial DNA (mtDNA) mutations are linked to human pathologies and mitochondrial function.
- Mitochondria play crucial roles in cellular energy production and regulation.
Purpose of the Study:
- To assess solar radiation-induced changes in mitochondrial integrity, function, and dynamics in human skin cells.
- To simulate summer sunlight intensity using a Q-Sun solar simulator.
Main Methods:
- Human skin cells (keratinocytes and fibroblasts) were exposed to simulated sunlight irradiation (SSI).
- Cells were evaluated for survival, viability, mitochondrial membrane potential (MMP), and mass post-exposure.
- Two exposure groups were used: single exposure and repeated exposures over seven days.
Main Results:
- Repeated SSI exposure decreased cell viability and survival in both keratinocytes and fibroblasts without recovery.
- Keratinocytes exhibited a periodic loss of MMP after single exposure and a dramatic loss after repeat exposure.
- Fibroblasts maintained MMP, but keratinocytes showed a significant decrease in mitochondrial mass after SSI.
Conclusions:
- Mitochondria in epidermal cells (keratinocytes) are more susceptible to sunlight damage than those in dermal cells (fibroblasts).
- This study confirms a skin layer-specific sensitivity to sunlight-induced mitochondrial damage.
- The findings highlight the differential impact of solar radiation on distinct skin cell types.
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